Oxidation-induced water-solubilization and chemical functionalization of fullerenes C60, Gd@C60 and Gd@C82: atomistic insights into the formation mechanisms and structures of fullerenols synthesized by different methods

Hierarchical Self-Assembly of Water-Soluble Fullerene Derivatives into Supramolecular Hydrogels

Controlling the self-assembly of nanoparticle building blocks into macroscale soft matter structures is an open question and of fundamental importance to fields as diverse as nanomedicine and next-generation energy storage. Within the vast library of nanoparticles, the fullerenes-a family of quasi-spherical carbon allotropes-are not explored beyond the most common, C60. Herein, a facile one-pot method is demonstrated for functionalizing fullerenes of different sizes (C60, C70, C84, and C90-92), yielding derivatives that self-assemble in aqueous solution into supramolecular hydrogels with distinct hierarchical structures. It is shown that the mechanical properties of these resultant structures vary drastically depending on the starting material. This work opens new avenues in the search for control of macroscale soft matter structures through tuning of nanoscale building blocks.

Functionalized Fullerenes and Their Applications in Electrochemistry, Solar Cells, and Nanoelectronics

Carbon-based nanomaterials have rapidly advanced over the last few decades. Fullerenes, carbon nanotubes, graphene and its derivatives, graphene oxide, nanodiamonds, and carbon-based quantum dots have been developed and intensively studied. Among them, fullerenes have attracted increasing research attention due to their unique chemical and physical properties, which have great potential in a wide range of applications. In this article, we offer a comprehensive review of recent progress in the synthesis and the chemical and physical properties of fullerenes and related composites. The review begins with the introduction of various methods for the synthesis of functionalized fullerenes. A discussion then follows on their chemical and physical properties. Thereafter, various intriguing applications, such as using carbon nanotubes as nanoreactors for fullerene chemical reactions, are highlighted. Finally, this review concludes with a summary of future research, major challenges to be met, and possible solutions.

Amphiphilic Aminated Derivatives of [60]Fullerene as Potent Inhibitors of Tumor Growth and Metastasis

Malignant proliferation and metastasis are the hallmarks of cancer cells. Aminated [70]fullerene exhibits notable antineoplastic effects, promoting it a candidate for multi-targeted cancer drugs. It is an urgent need to reveal the structure-activity relationship for antineoplastic aminated fullerenes. Herein, three amphiphilic derivatives of [60]fullerene with clarified molecular structures are synthesized: TAPC-4, TAPC-3, and TCPC-4. TAPC-4 inhibits the proliferation of diverse tumor cells via G0/G1 cell cycle arrest, reverses the epithelial-mesenchymal transition, and abrogates the high mobility of tumor cells. TAPC-4 can be excreted from the organism and achieves an in vivo inhibition index of 75.5% in tumor proliferation and 87.5% in metastatic melanoma with a wide safety margin. Molecular dynamics simulations reveal that the amphiphilic molecular structure and the ending amino groups promote the targeting of TAPC-4 to heat shock protein Hsp90-beta, vimentin, and myosin heavy chain 9 (MYH9), probably resulting in the alteration of cyclin D1 translation, vimentin expression, and MYH9 location, respectively. This work initially emphasizes the dominant role of the amphiphilic structure and the terminal amino moieties in the antineoplastic effects of aminated fullerenes, providing fundamental support for their anti-tumor drug development.

Metallofullerenols in biomedical applications

Metallofullerenols (MFs) are functionalized endohedral fullerenes connecting at least three levels of organization of matter: atomic, molecular, and supramolecular, resulting in their unique activity at the nanoscale. Biomedical applications of MFs started from gadolinium-containing contrasting agents, but today their potential medical applications go far beyond diagnostics and magnetic resonance imaging. In many cases, preclinical studies have shown a great therapeutic value of MFs, and here we provide an overview of interactions of MFs with high-energy radiation and with reactive oxygen species generated during radiation as a ground for potential applications in modern therapy of cancer patients. We also present the current knowledge on interactions of MFs with proteins and with other components of cells and tissues. Due to their antioxidant properties, as well as their ability to regulate the expression of genes involved in apoptosis, angiogenesis, and stimulation of the immune response, MFs can contribute to inhibition of tumor growth and protection of normal cells. MFs with enclosed gadolinium act as inhibitors of tumor growth in targeted therapy along with imaging techniques, but we hope that the data gathered in this review will help to accelerate further progress in the implementation of MFs, also the ones containing rare earth metals other than gadolinium, in a broad range of bioapplications covering not only diagnostics and bioimaging but also radiation therapy and cancer treatment by not-cytotoxic agents.

Functionalized Gadofullerene Ameliorates Impaired Glycolipid Metabolism in Type 2 Diabetic Mice

The soaring global prevalence of diabetes makes it urgent to explore new drugs with high efficacy and safety. Nanomaterial-derived bioactive agents are emerging as one of the most promising candidates for biomedical application. In the present study, we investigated the anti-diabetic effects of a functionalized gadofullerene (GF) using obese db/db and non-obese MKR mouse T2DM models. In both mouse models, the diabetic phenotypes including hyperglycemia, impaired glucose tolerance and insulin sensitivity were ameliorated following 2 or 4 weeks of i.p. administration of GF. GF lowered blood glucose levels in a dose-dependent manner. Importantly, the restored blood glucose levels could persist 10 days after withdrawal of GF treatment. The hepatic AKT/GSK3β/FoxO1 pathway is shown to be the main target of GF for re-balancing gluconeogenesis and glycogen synthesis in vivo and in vitro. In addition, GF treatment significantly reduced weight gain of db/db mice with reduced hepatic fat storage by the inhibition of de novo lipogenesis through mTOR/S6K/SREBP1 pathway. Our data provide compelling evidence to support the promising application of GF for the treatment of T2DM.

Antioxidant Potential of Aqueous Dispersions of Fullerenes C60, C70, and Gd@C82

The antioxidant potential (capacity and activity) of aqueous fullerene dispersions (AFD) of non-functionalized C60, C70, and Gd@C82 endofullerene (in micromolar concentration range) was estimated based on chemiluminescence measurements of the model of luminol and generation of organic radicals by 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP). The antioxidant capacity was estimated by the TRAP method, from the concentration of half-suppression, and from the suppression area in the initial period. All three approaches agree and show that the antioxidant capacity of AFDs increased in the order Gd@C82 < C70 < C60. Mathematical modeling of the long-term kinetics data was used for antioxidant activity estimation. The effect of C60 and C70 is found to be quenching of the excited product of luminol with ABAP-generated radical and not an actual antioxidant effect; quenching constants differ insignificantly. Apart from quenching with a similar constant, the AFD of Gd@C82 exhibits actual antioxidant action. The antioxidant activity in Gd@C82 is 300-fold higher than quenching constants.

Increasing the Resistance of Living Cells against Oxidative Stress by Nonnatural Surfactants as Membrane Guards

The importation of construction principles or even constituents from biology into materials science is a prevailing concept. Vice versa, the cellular level modification of living systems with nonnatural components is much more difficult to achieve. It has been done for analytical purposes, for example, imaging, to learn something about intracellular processes. Cases describing the improvement of a biological function by the integration of a nonnatural (nano)constituent are extremely rare. Because biological membranes contain some kind of a surfactant, for example, phospholipids, our idea is to modify cells with a newly synthesized surfactant. However, this surfactant is intended to possess an additional functionality, which is the reduction of oxidative stress. We report the synthesis of a surfactant with Janus-type head group architecture, a fullerene C₆₀ modified by five alkyl chains on one side and an average of 20 oxygen species on the other hemisphere. It is demonstrated that the amphiphilic properties of the fullerenol surfactant are similar to that of lipids. Not only quenching of reactive oxygen species (superoxide, hydroxyl radicals, peroxynitrite, and hydrogen peroxide) was successful, but also the fullerenol surfactant exceeds benchmark antioxidant agents such as quercetin. The surfactant was then brought into contact with different cell types, and the viability even of delicate cells such as human liver cells (HepG2) and human dopaminergic neurons (LUHMES) has proven to be extraordinarily high. We could show further that the cells take up the fullerenol surfactant, and as a consequence, they are protected much better against oxidative stress.

The antihyperlipidemic effects of fullerenol nanoparticles via adjusting the gut microbiota in vivo

BACKGROUND

Nanoparticles (NPs) administered orally will meet the gut microbiota, but their impacts on microbiota homeostasis and the consequent physiological relevance remain largely unknown. Here, we describe the modulatory effects and the consequent pharmacological outputs of two orally administered fullerenols NPs (Fol1 C60(OH)7(O)8 and Fol113 C60(OH)11(O)6) on gut microbiota.

RESULTS

Administration of Fol1 and Fol113 NPs for 4 weeks largely shifted the overall structure of gut microbiota in mice. The bacteria belonging to putative short-chain fatty acids (SCFAs)-producing genera were markedly increased by both NPs, especially Fol1. Dynamic analysis showed that major SCFAs-producers and key butyrate-producing gene were significantly enriched after treatment for 7-28 days. The fecal contents of SCFAs were consequently increased, which was accompanied by significant decreases of triglycerides and total cholesterol levels in the blood and liver, with Fol1 superior to Fol113. Under cultivation in vitro, fullerenols NPs can be degraded by gut flora and exhibited a similar capacity of inulin to promote SCFA-producing genera. The differential effects of Fol1 and Fol113 NPs on the microbiome may be attributable to their subtly varied surface structures.

CONCLUSIONS

The two fullerenol NPs remarkably modulate the gut microbiota and selectively enrich SCFA-producing bacteria, which may be an important reason for their anti-hyperlipidemic effect in mice.

Epoxy and Oxidoannulene Oxidation Mechanisms of Fused-Pentagon Chlorofullerenes: Oxides Linked by a Pirouette-Type Transition State

Recently, the oxidative functionalization of double-fused-pentagon (DFP)-containing chlorofullerenes ^#271C₅₀Cl₁₀ and ^#913C₅₆Cl₁₀ was carried out, resulting in two monoepoxides with the oxygen atom added at the ortho site of pentalene on the DFP moiety. To uncover the reactivity of isolated-pentagon-rule violating fullerenes upon oxidation, two possible formation processes (ozone molecule and oxygen radical served as oxidation reagents) of these two oxides were systematically investigated through density functional theory calculations. For the ozone oxidation, two possible pathways were explored, and the results indicate that the biradical mechanism Path_os-RACDP is kinetically more favorable than Path_os-RABP, where R, A, and P represent reactants, ozonide intermediates, and oxidation products and B, C, and D represent another three oxygen-containing intermediates. The products obtained by ozone oxidation ([6,6]-55-closed epoxides P-C₃-C₂₉ for ^#271C₅₀Cl₁₀ and P-C₄₂-C₄₃ for ^#913C₅₆Cl₁₀ with oxygen atom added at the shortest and highest HOMO-contribution bonds) are consistent with experimental observations. However, the oxygen radical additions on these two chlorofullerenes favor generation of the [5,6]-66-open oxidoannulene adducts P-C₃-C₂ and P-C₄₂-C₅₄, respectively. Subsequent analyses of their geometrical features and structural stabilities suggest that these two oxidoannulene adducts are energetically unfavorable and could be converted to more stable epoxides mentioned above by undergoing a pirouette-type transition state. In these two diverse oxidation procedures, the favorable C-C bonds for ozone attacking and C atoms for oxygen-adsorption are rationalized in terms of their bond lengths and HOMO contributions as well as pyramidalization angles.

Which fullerenols are water soluble? Systematic atomistic investigation

Insights to guide a choice of most soluble fullerenols.

Gd@C82-(ethylenediamine)8 Nanoparticle: A New High-Efficiency Water-Soluble ROS Scavenger

It is important to maintain a reactive oxygen species (ROS) balance in organisms; thus, a valid ROS scavenger with good biocompatibility is urgently required. To prepare a high-efficiency ROS scavenger, multiple ethylenediamine (EDA) groups are bonded for the first time to a metallofullerene Gd@C₈₂ to obtain water-soluble Gd@C₈₂-(EDA)₈ nanoparticles (NPs) through a facile solid-liquid reaction. Gd@C₈₂-(EDA)₈ NPs with a relatively better conjugation possess an excellent capability to scavenge hydroxyl radicals. Moreover, Gd@C₈₂-(EDA)₈ NPs exhibited a remarkable cytoprotective effect against H₂O₂-induced injuries to human epidermal keratinocytes-adult (HEK-a) cells at a low concentration of 2.5 μM. In contrast, Gd@C₈₂-(OH)₂₆ NPs that modified with hydroxyls show an apparent protective effect at a much higher concentration of 40 μM. This outstanding cytoprotective performance of Gd@C₈₂-(EDA)₈ NPs is mainly attributed to their extremely high cellular uptake and comparably strong conjugation. Gd@C₈₂-(EDA)₈ NPs with good biocompatibility exhibit excellent ROS scavenging capability even at a significantly low concentration, which promotes its versatile applications in cosmetics and biomedicine.

Regioselective Oxidation of Fused-Pentagon Chlorofullerenes

Two monoxides of typical smaller chlorofullerenes, (#271)C50Cl10O and (#913)C56Cl10O, featured with double-fused-pentagons, were synthesized to demonstrate further regioselective functionalization of non-IPR (IPR = isolated pentagon rule) chlorofullerenes. Both non-IPR chlorofullerene oxides exhibit an epoxy structure at the ortho-site of fused pentagons. In terms of the geometrical analysis and theoretical calculations, the principles for regioselective epoxy oxidation of non-IPR chlorofullerenes are revealed to follow both "fused-pentagon ortho-site" and "olefinic bond" rules, which are valuable for prediction of oxidation of non-IPR chlorofullerenes.